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ISRO’s July 2026 Double Redemption: PSLV-C63 Return-to-Flight & GISAT-2 Launch
Key Takeaways (Prelims Catalyst)
- PSLV Failures: PSLV-C61 (May 2025) and PSLV-C62 (Jan 2026) — both traced to anomalies in the PS3 solid motor stage
- Root Cause: Manufacturing defects in solid propellant (HTPB) leading to chamber pressure loss and roll-rate disturbance
- July 2026 Missions: PSLV-C63 (Return-to-Flight) with TDS-01 + GSLV Mk II with GISAT-2 (EOS-05)
- TDS-01 Payloads: High-Thrust Electric Propulsion, Indigenous TWTA, and Quantum Key Distribution (QKD)
- GISAT-2 Orbit: Geostationary Orbit (GEO) at 35,786 km — stays fixed over India
- GISAT-2 Capability: Scans entire India every 30 minutes; targeted areas every 5 minutes with hyperspectral imaging
- PSLV Stages: Solid (PS1 & PS3) vs Liquid (PS2 & PS4) — solid motors cannot be throttled or shut down once ignited
- Strategic Importance: GISAT-2 provides real-time maritime surveillance for the Indian Navy and rapid disaster response
- PSLV-N1: First fully industry-built PSLV (by HAL + L&T under NSIL)
Table of Contents
Introduction: ISRO’s July 2026 Double-Header
After suffering back-to-back failures in May 2025 (PSLV-C61) and January 2026 (PSLV-C62), ISRO is attempting a high-stakes comeback in July 2026 with two major missions: the PSLV-C63 Return-to-Flight and the launch of GISAT-2 (EOS-05) on the GSLV Mk II. These missions are critical not only for restoring confidence in the PSLV but also for enhancing India’s real-time earth observation and maritime surveillance capabilities.
1. The PSLV Crisis: C61 & C62 Failures
PSLV-C61 (May 18, 2025)
Payload: EOS-09 (Synthetic Aperture Radar satellite)
Failure: Third stage (PS3) suffered sudden loss of combustion chamber pressure after ignition. The vehicle could not achieve the required velocity and fell back into the ocean.
PSLV-C62 (January 12, 2026)
Payload: Anvesha (Hyperspectral satellite) + 16 commercial satellites
Failure: During PS3 burn, the vehicle experienced violent roll-rate disturbance (uncontrolled spinning), overwhelming the attitude control system and leading to mission failure.
2. The PS3 Solid Motor Problem
Both failures originated in the PS3 solid rocket motor (third stage), which uses HTPB (Hydroxyl-terminated polybutadiene) propellant.
| Stage | Propulsion Type | Propellant | Key Characteristic |
|---|---|---|---|
| PS1 | Solid | HTPB | Cannot be throttled or shut down once ignited |
| PS2 | Liquid | UDMH + N2O4 (Vikas Engine) | Controllable and steerable |
| PS3 | Solid | HTPB | Operates in near-vacuum; critical for reaching orbital velocity |
| PS4 | Liquid | MMH + MON | Highly precise orbital injection |
Root Causes Identified:
- Internal cracks/voids in the solid propellant grain or bonding failure with the casing → sudden drop in chamber pressure
- Defects in the flex-nozzle control system → asymmetrical thrust causing violent rolling
Fixes Implemented for July 2026:
- Advanced Non-Destructive Testing (X-ray CT scans) for every solid motor
- Upgraded carbon-carbon composite nozzle liners
- Enhanced attitude control margins to handle larger roll torques
3. PSLV-C63 Return-to-Flight Mission
Payload: TDS-01 (Technology Demonstration Satellite)
Key Technologies Being Tested:
- High-Thrust Electric Propulsion System (Xenon Ion): More efficient than chemical propulsion for orbit maintenance
- Indigenous Travelling Wave Tube Amplifier (TWTA): Critical for satellite communication (previously imported)
- Quantum Key Distribution (QKD) Payload: Demonstrates unhackable space-to-ground quantum encryption
Strategic Importance: This mission qualifies critical indigenous technologies for future deep-space and secure communication missions.
4. GISAT-2 (EOS-05): Eyes in Geostationary Orbit
LEO vs GEO Comparison
| Parameter | LEO Satellites (e.g. Cartosat) | GISAT-2 (GEO) |
|---|---|---|
| Altitude | 500–800 km | 35,786 km |
| Revisit Time | Once or twice a day | Entire India every 30 min; targeted areas every 5 min |
| Spatial Resolution | Very High | Moderate (42m multispectral) |
| Temporal Resolution | Low | Extremely High |
| Best For | High-detail mapping | Real-time monitoring & rapid response |
GISAT-2 Capabilities
- 700 mm Ritchey-Chrétien Telescope
- Multispectral (VNIR): 6 channels, 42m resolution
- Hyperspectral (VNIR): 158 channels, 318m resolution
- Hyperspectral (SWIR): 256 channels, 191m resolution
Why Hyperspectral Matters: It can detect camouflaged military assets, crop health, mineral deposits, and environmental changes by reading the unique “spectral signature” of materials.
Strategic & Civilian Importance
- Disaster Management: Real-time tracking of cyclones, floods, and forest fires
- Military: Continuous maritime domain awareness over the Indian Ocean Region (IOR)
- Complements: GSAT-7 (Rukmini) and GSAT-7R naval communication satellites
Practice MCQs for UPSC, SSC & State PSC
Q1. The PSLV failures in 2025 and 2026 were primarily attributed to issues in which stage?
Options:
A) PS1 (First Stage)
B) PS2 (Second Stage)
C) PS3 (Third Stage)
D) PS4 (Fourth Stage)
Answer: C) PS3 (Third Stage)
Explanation: Both failures originated in the PS3 solid rocket motor due to manufacturing defects in the propellant grain and nozzle system.
Q2. What type of propellant is used in the PS3 stage of PSLV?
Options:
A) Liquid (UDMH + N2O4)
B) Solid (HTPB)
C) Cryogenic (Liquid Hydrogen + Liquid Oxygen)
D) Hybrid
Answer: B) Solid (HTPB)
Explanation: The PS3 stage uses Hydroxyl-terminated polybutadiene (HTPB), a solid propellant that cannot be throttled or shut down once ignited.
Q3. What is the primary advantage of placing GISAT-2 in Geostationary Orbit?
Options:
A) Higher spatial resolution than LEO satellites
B) Ability to remain fixed over the same geographical area
C) Lower launch cost
D) Better coverage of polar regions
Answer: B) Ability to remain fixed over the same geographical area
Explanation: In GEO, the satellite’s orbital period matches Earth’s rotation, allowing continuous monitoring of the Indian subcontinent.
Q4. Which technology is NOT being tested on the TDS-01 satellite?
Options:
A) High-Thrust Electric Propulsion (Xenon Ion)
B) Indigenous Travelling Wave Tube Amplifier (TWTA)
C) Quantum Key Distribution (QKD)
D) Synthetic Aperture Radar (SAR)
Answer: D) Synthetic Aperture Radar (SAR)
Explanation: TDS-01 is testing Electric Propulsion, Indigenous TWTA, and QKD. SAR was the payload on the failed EOS-09 mission.
Q5. What is the revisit capability of GISAT-2 for targeted disaster zones?
Options:
A) Every 30 minutes
B) Every 5 minutes
C) Once per day
D) Every 2 hours
Answer: B) Every 5 minutes
Explanation: GISAT-2 can scan the entire Indian landmass every 30 minutes and focus on specific crisis zones with a 5-minute revisit time.
Q6. Which organization is building the PSLV-N1 (EOS-10) launch vehicle?
Options:
A) ISRO alone
B) HAL and L&T under NSIL
C) DRDO
D) Antrix Corporation
Answer: B) HAL and L&T under NSIL
Explanation: PSLV-N1 will be the first PSLV fully built by an Indian industry consortium (HAL + L&T) under NewSpace India Limited (NSIL).
Q7. What is the main advantage of Hyperspectral imaging used in GISAT-2?
Options:
A) It provides very high spatial resolution
B) It can identify materials by their unique spectral signatures
C) It works only during daytime
D) It is cheaper than multispectral imaging
Answer: B) It can identify materials by their unique spectral signatures
Explanation: Hyperspectral sensors divide light into hundreds of narrow bands, allowing detection of camouflaged targets, crop health, and mineral deposits based on how different materials reflect specific wavelengths.
Frequently Asked Questions
Why did the PSLV fail in May 2025 and January 2026?
Both failures were traced to manufacturing defects in the PS3 solid rocket motor (third stage), leading to sudden loss of chamber pressure and uncontrolled rolling of the vehicle.
What is the significance of the PSLV-C63 mission?
PSLV-C63 is the Return-to-Flight mission that will validate the fixes made to the PS3 solid motor. It also carries the TDS-01 satellite to test critical indigenous technologies like Electric Propulsion, TWTA, and Quantum Key Distribution.
What makes GISAT-2 different from normal earth observation satellites?
GISAT-2 is placed in Geostationary Orbit (35,786 km), allowing it to remain fixed over India. It can scan the entire country every 30 minutes and specific areas every 5 minutes with hyperspectral imaging capabilities.
What is Hyperspectral imaging and why is it useful?
Hyperspectral imaging splits light into hundreds of narrow spectral bands. This allows the satellite to identify materials (including camouflaged military assets) by reading their unique “spectral signatures,” which standard cameras cannot do.
Which organization is building the PSLV-N1 rocket?
PSLV-N1 (EOS-10) will be the first PSLV fully manufactured by an Indian industry consortium consisting of Hindustan Aeronautics Limited (HAL) and Larsen & Toubro (L&T) under the guidance of NewSpace India Limited (NSIL).
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